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Dieting safe for pregnant overweight women, study concludes

Findings contradict NICE guidance, which says baby’s health may be harmed

Caroline White

Friday, 18 May 2012

Pregnant women can safely diet during pregnancy to combat excess weight gain, without harming the health of their unborn child, finds research published on bmj.com.

And for those who are already overweight or obese when they conceive, a calorie controlled diet can reduce the risk of serious complications such as pre-eclampsia, gestational diabetes, and premature birth, without any risk to their unborn child, say the authors.

But the findings, which are based on a systematic review of 44 trials of weight loss interventions, involving over 7000 women, contradict NICE guidance.

Published in 2010, this concluded that dieting during pregnancy was not to be recommended as it could harm the health of the developing baby.

In the UK, more than half the women of reproductive age are overweight or obese, and in the US, up to 40% of women gain more than the recommended weight in pregnancy. Excess weight gain during pregnancy is associated with several serious health problems.

The researchers investigated the effects of diet, exercise, or a combination of the two on weight gain during pregnancy and any adverse effects on mother or baby, drawing on published research.

They found that weight management interventions in pregnancy worked and reduced weight gain in the mother, with dieting achieving the largest average reduction in weight gain (almost 4 kg) compared with just 0.7 kg for exercise and 1 kg for a combination of the two.

A calorie controlled diet was also best for preventing pregnancy complications such as pre-eclampsia, diabetes, high blood pressure, and premature birth, although the evidence was not strong, the authors emphasise.

Importantly, the results showed that interventions are safe and do not adversely affect the baby’s weight, prompting the authors to conclude that dietary and lifestyle interventions in pregnancy improve outcomes for both mother and baby.

But they acknowledge the lack of data on risk factors such as age, ethnicity and socioeconomic status.

However, in an accompanying editorial, experts at St Thomas’ Hospital, London, say there is not yet sufficient evidence to support any particular approach.

Lucilla Poston and Lucy Chappell suggest that although this study is “timely and welcome”, it does not provide the evidence needed for NICE to reassess its guidelines for weight management in pregnancy. Several ongoing trials should provide some answers to the most effective interventions in overweight and obese women during pregnancy, they say.

Health professionals should take the opportunity to discuss weight management as mothers are motivated to make changes that will benefit themselves and their baby, say the study authors.

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